We propose to acquire an Applied Biosystems Sciex QTRAP 5500 hybrid triple quadrupole-linear ion trap mass spectrometer (MS) for LC/MS/MS analyses of biomedically important complex lipids. This program will benefit from the sensitivity and versatility of this contemporary instrument, which can be operated as a triple quadrupole capable of performing tandem scanning modes that have proven invaluable in our analyses of lipids in biological specimens. Our existing triple quadrupole MS is an older instrument that is becoming difficult to maintain and lacks the sensitivity of contemporary instruments. The third quadrupole of the requested instrument can also be operated as a linear ion trap (LIT), permitting its use in a tandem quadrupole-LIT configuration that permits extremely high sensitivity MSn experiments for lipid structural determinations. The requested instrument is to be placed in Site 1 of the Washington University (WU) Medicine Department MS Facility, which is one site of the NCRR-supported WU Biomedical MS Resource (P41-RR00954) and also serves as a core MS laboratory for the WU Diabetes Research and Training Center (DRTC, P60-DK20579) and the WU Clinical Nutrition Research Unit (CNRU, P30-DK56341) that are supported by NIDDK. This facility thus serves a wide range of NIH-funded investigators here and elsewhere. The instrument will be equipped with a nanospray source interfaced with a nano-HPLC, and this system will provide a platform for separation and analysis of complex lipid molecules relevant to the pathogenesis of metabolic diseases such as diabetes mellitus and its complications, to HIV/AIDS, to neurophysiologic research, and to characterizing components of cell envelopes of pathogenic microorganisms that govern their virulence. A specific aim is to further the NIH-funded research of the many users of our MS facility who study biomedically important lipids, and eight major projects are described in this application as examples: (1) Phospholipid-derived mediators and insulin secretion, glucose tolerance, and atherogenesis (Dr. John Turk, WU);(2) Phospholipid hydrolysis and ER stress-induced apoptosis of pancreatic islet ?-cells (Dr. Sasanka Ramanadham, WU);(3) Using Drosophila to identify candidate modifiers of glucose toxicity (Dr. Thomas Baranski, WU);(4) Role of glycoconjugates and sphingolipids in kinetoplastid parasite growth and virulence (Dr. Steven Beverley, WU, and Dr. James Bangs, Univ. Wisconsin-Madison);(5) Molecular bases of antimicrobial resistance and virulence in pathogenic Salmonella gram-negative bacteria (Dr. Eduardo Groisman, WU, and Dr. Yixin Shi, Univ. Arizona-Tempe);(6) Mycobacterium tuberculosis cell wall lipid molecular species and cellular mechanisms of destructive host tissue reactions in a murine granuloma model (Dr. David Russell, Cornell Univ.);(7) Neural mechanisms of olfactory pattern recognition (Dr. Timothy Holy, WU);and (8) HIV-infection and lipid biochemistry (Dr. Kevin Yarasheski and Dr. David Clifford, WU). PUBLIC HEALTH RELEVANCE: The requested Applied Biosciences Sciex QTRAP 5500 mass spectrometer will be used to perform measurements on biological materials that will provide information on several important biomedical problems that are relevant to diabetes, cardiovascular disease, infectious disease, brain function, and AIDS. These include mechanisms regulating the function and survival of insulin-secreting beta cells, properties of the cell surfaces of pathogenic microorganisms that govern their ability to infect and kill humans, and why patients with AIDS develop diseases of the heart and blood vessels prematurely. Such information will provide insight into developing new ways to diagnose and treat human diseases and thereby improve human health.